In recent years, research and development are underway of upsizing of organic electroluminescence (EL) display panels, which are display panels making use of light-emission of organic EL elements. Typically, an organic EL display panel has an array of organic EL elements disposed above a support substrate, and displays an image by the organic EL elements (pixels) emitting light. A typical organic EL element includes a pair of electrodes, and a functional layer containing functional material, such as an organic light-emitting layer containing organic light-emitting material, disposed between the electrodes. Meanwhile, in manufacturing a full-color compatible organic EL display panel, separate application of three different organic light-emitting materials, each emitting a different one of the colors red, green, and blue, is now typically carried out. This is advantageous in terms of luminous efficacy, light-emission lifetime, color representation, and the like. Further, there are functional layers other than organic light-emitting layers, which include hole injection layers, electron injection layers, hole transport layers, electron transport layers, hole blocking layers, electron blocking layers, and buffer layers. The function of a given functional layer in an organic EL element is dependent upon the functional material contained in the functional layer and the position of the functional layer in the organic EL element.
Typically, methods used in forming functional layers are largely divided into dry processes and wet processes. One example of a dry process is vacuum vapor deposition, and one example of a wet process is inkjet printing. A wet process typically involves the application of ink containing functional material, and the drying of the ink. Wet processes are considered as being more suitable than dry processes for large-sized organic EL display panels manufactured through separate application of three different organic light-emitting materials each corresponding to a different color, for achieving accurate forming of functional layers, efficient material use, and the like.
When employing a wet process, a bank layer defining apertures is formed on a substrate to prevent ink outflow from predetermined ink application positions, and ink is applied to each of such apertures. Typically, a bank layer is made of a photoresist, and is formed through photolithography. Specifically, the forming of a bank layer involves, for example, application of a photoresist onto a substrate, exposure using a mask (referred to in the following as masked exposure), developing, and baking of the photoresist (refer to Patent Literatures 1, 2, and 3, for example).
Among such processes, baking of developed photoresist is performed to provide a bank layer with resistance against organic solvents, and thereby prevents deterioration of the bank layer due to contact with ink used in the wet process (refer to Patent Literature 1 for example). In addition, the baking, when performed in the forming of a bank layer containing a liquid repellent component, causes movement of the liquid repellent component to the bank layer surface, and thus increases the liquid repellency of the bank layer surface (refer to Patent Literature 2, for example).